Loans and Allowances for Credit Losses, Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	$ 648,501
Financing Receivable, Originated, 2019	3,353,429
Financing Receivable, Originated, 2018	2,971,436
Financing Receivable, Originated, 2017	2,224,426
Financing Receivable, Originated, 2016	1,566,422
Financing Receivable, Originated, 2015 or Prior	3,751,693
Financing Receivable, Revolving	7,570,674
Financing Receivable, Revolving, Converted to Term Loan	377,389
Total	22,463,970
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		$ 19,826,731
Non-Graded, Recorded Investment		1,924,256
Total	22,463,970	21,750,987
Related Allowance [Abstract]
Internally Risk Graded, Allowance		179,129
Non-Graded, Allowance		14,435
Total	315,311	210,759	$ 205,340	$ 207,457
Commercial [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	353,763
Financing Receivable, Originated, 2019	1,815,289
Financing Receivable, Originated, 2018	1,628,731
Financing Receivable, Originated, 2017	1,244,748
Financing Receivable, Originated, 2016	847,499
Financing Receivable, Originated, 2015 or Prior	2,091,690
Financing Receivable, Revolving	6,795,876
Financing Receivable, Revolving, Converted to Term Loan	18,379
Total	14,795,975
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		13,997,538
Non-Graded, Recorded Investment		34,112
Total	14,795,975	14,031,650
Related Allowance [Abstract]
Internally Risk Graded, Allowance		117,236
Non-Graded, Allowance		951
Total	213,438	118,187	103,577	102,226
Commercial [Member] | Energy [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	2,285
Financing Receivable, Originated, 2019	111,236
Financing Receivable, Originated, 2018	85,206
Financing Receivable, Originated, 2017	15,377
Financing Receivable, Originated, 2016	1,564
Financing Receivable, Originated, 2015 or Prior	45,822
Financing Receivable, Revolving	3,850,186
Financing Receivable, Revolving, Converted to Term Loan	0
Total	4,111,676
Recorded Investment [Abstract]
Total	4,111,676	3,973,377
Commercial [Member] | Healthcare [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	131,031
Financing Receivable, Originated, 2019	619,122
Financing Receivable, Originated, 2018	631,928
Financing Receivable, Originated, 2017	484,768
Financing Receivable, Originated, 2016	250,555
Financing Receivable, Originated, 2015 or Prior	838,232
Financing Receivable, Revolving	209,433
Financing Receivable, Revolving, Converted to Term Loan	27
Total	3,165,096
Recorded Investment [Abstract]
Total	3,165,096	3,033,916
Commercial [Member] | Services [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	65,471
Financing Receivable, Originated, 2019	541,631
Financing Receivable, Originated, 2018	532,402
Financing Receivable, Originated, 2017	460,686
Financing Receivable, Originated, 2016	421,127
Financing Receivable, Originated, 2015 or Prior	918,379
Financing Receivable, Revolving	1,013,458
Financing Receivable, Revolving, Converted to Term Loan	2,594
Total	3,955,748
Recorded Investment [Abstract]
Total	3,955,748	3,122,163
Commercial [Member] | General business [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	154,976
Financing Receivable, Originated, 2019	543,300
Financing Receivable, Originated, 2018	379,195
Financing Receivable, Originated, 2017	283,917
Financing Receivable, Originated, 2016	174,253
Financing Receivable, Originated, 2015 or Prior	289,257
Financing Receivable, Revolving	1,722,799
Financing Receivable, Revolving, Converted to Term Loan	15,758
Total	3,563,455
Recorded Investment [Abstract]
Total	3,563,455
Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Total		1,760,866
Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Total		665,449
Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Total		709,868
Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Total		766,011
Commercial real estate [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	187,958
Financing Receivable, Originated, 2019	1,085,183
Financing Receivable, Originated, 2018	1,050,268
Financing Receivable, Originated, 2017	618,601
Financing Receivable, Originated, 2016	391,320
Financing Receivable, Originated, 2015 or Prior	885,160
Financing Receivable, Revolving	231,553
Financing Receivable, Revolving, Converted to Term Loan	42
Total	4,450,085
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		4,433,783
Non-Graded, Recorded Investment		0
Total	4,450,085	4,433,783
Related Allowance [Abstract]
Internally Risk Graded, Allowance		51,805
Non-Graded, Allowance		0
Total	51,461	51,805	58,134	60,026
Commercial real estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Total		150,879
Commercial real estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Total		775,521
Commercial real estate [Member] | Office [Member]
Recorded Investment [Abstract]
Total		928,379
Commercial real estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Total		1,265,562
Commercial real estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Total		856,117
Commercial real estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Total		457,325
Loans to individuals [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	106,780
Financing Receivable, Originated, 2019	452,957
Financing Receivable, Originated, 2018	292,437
Financing Receivable, Originated, 2017	361,077
Financing Receivable, Originated, 2016	327,603
Financing Receivable, Originated, 2015 or Prior	774,843
Financing Receivable, Revolving	543,245
Financing Receivable, Revolving, Converted to Term Loan	358,968
Total	3,217,910
Recorded Investment [Abstract]
Total	3,217,910	2,084,172
Related Allowance [Abstract]
Total	50,412
Loans to individuals [Member] | Permanent Residential Mortgage [Member]
Recorded Investment [Abstract]
Total		1,057,321
Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member]
Recorded Investment [Abstract]
Total		197,794
Loans to individuals [Member] | Home Equity Loan [Member]
Recorded Investment [Abstract]
Total		829,057
Loans to individuals [Member] | Residential mortgage [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	58,635
Financing Receivable, Originated, 2019	216,265
Financing Receivable, Originated, 2018	196,001
Financing Receivable, Originated, 2017	232,074
Financing Receivable, Originated, 2016	223,519
Financing Receivable, Originated, 2015 or Prior	524,851
Financing Receivable, Revolving	37,242
Financing Receivable, Revolving, Converted to Term Loan	355,968
Total	1,844,555
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		279,113
Non-Graded, Recorded Investment		1,805,059
Total	1,844,555	2,084,172
Related Allowance [Abstract]
Internally Risk Graded, Allowance		3,085
Non-Graded, Allowance		11,315
Total		14,400	15,668	17,964
Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	1,459
Financing Receivable, Originated, 2018	8,321
Financing Receivable, Originated, 2017	13,353
Financing Receivable, Originated, 2016	28,986
Financing Receivable, Originated, 2015 or Prior	145,770
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total	197,889
Recorded Investment [Abstract]
Total	197,889
Loans to individuals [Member] | Personal [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	48,145
Financing Receivable, Originated, 2019	235,233
Financing Receivable, Originated, 2018	88,115
Financing Receivable, Originated, 2017	115,650
Financing Receivable, Originated, 2016	75,098
Financing Receivable, Originated, 2015 or Prior	104,222
Financing Receivable, Revolving	506,003
Financing Receivable, Revolving, Converted to Term Loan	3,000
Total	1,175,466
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,116,297
Non-Graded, Recorded Investment		85,085
Total	1,175,466	1,201,382
Related Allowance [Abstract]
Internally Risk Graded, Allowance		7,003
Non-Graded, Allowance		2,169
Total		9,172	8,783	9,473
Specific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		19,826,731
Non-Graded, Recorded Investment		1,924,256
Total		21,750,987
Related Allowance [Abstract]
Internally Risk Graded, Allowance		179,129
Non-Graded, Allowance		14,435
Total		193,564
Nonspecific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Non-Graded, Recorded Investment		0
Total		0
Related Allowance [Abstract]
Internally Risk Graded, Allowance		0
Non-Graded, Allowance		0
Total		17,195	$ 19,178	$ 17,768
Performing [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		1,886,858
Performing [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		19,312,702
Performing [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		210,149
Performing [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		160,326
Performing [Member] | Commercial [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		34,075
Performing [Member] | Commercial [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		13,538,705
Performing [Member] | Commercial [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		187,881
Performing [Member] | Commercial [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		155,573
Performing [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Energy [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	2,285
Financing Receivable, Originated, 2019	107,434
Financing Receivable, Originated, 2018	74,946
Financing Receivable, Originated, 2017	15,377
Financing Receivable, Originated, 2016	1,506
Financing Receivable, Originated, 2015 or Prior	3,484
Financing Receivable, Revolving	3,505,123
Financing Receivable, Revolving, Converted to Term Loan	0
Total	3,710,155
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		3,700,406
Performing [Member] | Commercial [Member] | Energy [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	10,260
Financing Receivable, Originated, 2017	0
Financing Receivable, Originated, 2016	0
Financing Receivable, Originated, 2015 or Prior	0
Financing Receivable, Revolving	118,222
Financing Receivable, Revolving, Converted to Term Loan	0
Total	128,482
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		117,298
Performing [Member] | Commercial [Member] | Energy [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	0
Financing Receivable, Originated, 2016	58
Financing Receivable, Originated, 2015 or Prior	13,439
Financing Receivable, Revolving	163,094
Financing Receivable, Revolving, Converted to Term Loan	0
Total	176,591
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		63,951
Performing [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Healthcare [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	131,002
Financing Receivable, Originated, 2019	615,580
Financing Receivable, Originated, 2018	623,438
Financing Receivable, Originated, 2017	479,985
Financing Receivable, Originated, 2016	250,320
Financing Receivable, Originated, 2015 or Prior	806,699
Financing Receivable, Revolving	205,384
Financing Receivable, Revolving, Converted to Term Loan	27
Total	3,112,435
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		2,995,514
Performing [Member] | Commercial [Member] | Healthcare [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	3,782
Financing Receivable, Originated, 2016	178
Financing Receivable, Originated, 2015 or Prior	19,133
Financing Receivable, Revolving	3,515
Financing Receivable, Revolving, Converted to Term Loan	0
Total	26,608
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		13,117
Performing [Member] | Commercial [Member] | Healthcare [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	3,505
Financing Receivable, Originated, 2018	7,955
Financing Receivable, Originated, 2017	1,001
Financing Receivable, Originated, 2016	57
Financing Receivable, Originated, 2015 or Prior	9,465
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total	21,983
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		20,805
Performing [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Services [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	65,471
Financing Receivable, Originated, 2019	529,831
Financing Receivable, Originated, 2018	512,549
Financing Receivable, Originated, 2017	441,302
Financing Receivable, Originated, 2016	407,067
Financing Receivable, Originated, 2015 or Prior	899,776
Financing Receivable, Revolving	987,628
Financing Receivable, Revolving, Converted to Term Loan	2,594
Total	3,846,218
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		3,050,946
Performing [Member] | Commercial [Member] | Services [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	1,125
Financing Receivable, Originated, 2018	18,071
Financing Receivable, Originated, 2017	13,977
Financing Receivable, Originated, 2016	4,219
Financing Receivable, Originated, 2015 or Prior	10,963
Financing Receivable, Revolving	10,715
Financing Receivable, Revolving, Converted to Term Loan	0
Total	59,070
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		29,943
Performing [Member] | Commercial [Member] | Services [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	10,675
Financing Receivable, Originated, 2018	1,782
Financing Receivable, Originated, 2017	2,774
Financing Receivable, Originated, 2016	8,674
Financing Receivable, Originated, 2015 or Prior	3,709
Financing Receivable, Revolving	14,421
Financing Receivable, Revolving, Converted to Term Loan	0
Total	42,035
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		33,791
Performing [Member] | Commercial [Member] | General business [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	154,807
Financing Receivable, Originated, 2019	525,223
Financing Receivable, Originated, 2018	365,108
Financing Receivable, Originated, 2017	271,723
Financing Receivable, Originated, 2016	165,711
Financing Receivable, Originated, 2015 or Prior	278,923
Financing Receivable, Revolving	1,705,114
Financing Receivable, Revolving, Converted to Term Loan	15,600
Total	3,482,209
Performing [Member] | Commercial [Member] | General business [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	7,382
Financing Receivable, Originated, 2018	3,259
Financing Receivable, Originated, 2017	6,530
Financing Receivable, Originated, 2016	1,003
Financing Receivable, Originated, 2015 or Prior	5,168
Financing Receivable, Revolving	7,387
Financing Receivable, Revolving, Converted to Term Loan	138
Total	30,867
Performing [Member] | Commercial [Member] | General business [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	169
Financing Receivable, Originated, 2019	8,715
Financing Receivable, Originated, 2018	5,900
Financing Receivable, Originated, 2017	4,564
Financing Receivable, Originated, 2016	6,195
Financing Receivable, Originated, 2015 or Prior	5,005
Financing Receivable, Revolving	10,144
Financing Receivable, Revolving, Converted to Term Loan	6
Total	40,698
Performing [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Wholesale/retail [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,749,023
Performing [Member] | Commercial [Member] | Wholesale/retail [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		5,281
Performing [Member] | Commercial [Member] | Wholesale/retail [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		5,399
Performing [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Manufacturing [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		623,219
Performing [Member] | Commercial [Member] | Manufacturing [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		18,214
Performing [Member] | Commercial [Member] | Manufacturing [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		13,883
Performing [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Public finance [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		709,868
Performing [Member] | Commercial [Member] | Public finance [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Public finance [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		34,075
Performing [Member] | Commercial [Member] | Other commercial and industrial [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		709,729
Performing [Member] | Commercial [Member] | Other commercial and industrial [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		4,028
Performing [Member] | Commercial [Member] | Other commercial and industrial [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		17,744
Performing [Member] | Commercial real estate [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	187,958
Financing Receivable, Originated, 2019	1,085,148
Financing Receivable, Originated, 2018	1,049,257
Financing Receivable, Originated, 2017	599,480
Financing Receivable, Originated, 2016	382,196
Financing Receivable, Originated, 2015 or Prior	880,706
Financing Receivable, Revolving	231,526
Financing Receivable, Revolving, Converted to Term Loan	42
Total	4,416,313
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		4,381,663
Performing [Member] | Commercial real estate [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	12,167
Financing Receivable, Originated, 2016	1,640
Financing Receivable, Originated, 2015 or Prior	3,152
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total	16,959
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		22,145
Performing [Member] | Commercial real estate [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	35
Financing Receivable, Originated, 2018	1,011
Financing Receivable, Originated, 2017	6,722
Financing Receivable, Originated, 2016	0
Financing Receivable, Originated, 2015 or Prior	473
Financing Receivable, Revolving	27
Financing Receivable, Revolving, Converted to Term Loan	0
Total	8,268
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		2,349
Performing [Member] | Commercial real estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Residential construction and land development [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		150,529
Performing [Member] | Commercial real estate [Member] | Residential construction and land development [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Residential construction and land development [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Retail [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		743,343
Performing [Member] | Commercial real estate [Member] | Retail [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		12,067
Performing [Member] | Commercial real estate [Member] | Retail [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,243
Performing [Member] | Commercial real estate [Member] | Office [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Office [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		923,202
Performing [Member] | Commercial real estate [Member] | Office [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		5,177
Performing [Member] | Commercial real estate [Member] | Office [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Multifamily [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,257,005
Performing [Member] | Commercial real estate [Member] | Multifamily [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,604
Performing [Member] | Commercial real estate [Member] | Multifamily [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		95
Performing [Member] | Commercial real estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Industrial [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		852,539
Performing [Member] | Commercial real estate [Member] | Industrial [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,658
Performing [Member] | Commercial real estate [Member] | Industrial [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,011
Performing [Member] | Commercial real estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		0
Performing [Member] | Commercial real estate [Member] | Other commercial real estate [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		455,045
Performing [Member] | Commercial real estate [Member] | Other commercial real estate [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,639
Performing [Member] | Commercial real estate [Member] | Other commercial real estate [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		758,260
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		276,138
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		78
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		2,404
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		191,694
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Home Equity Loan [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		817,976
Performing [Member] | Loans to individuals [Member] | Home Equity Loan [Member] | Pass [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Home Equity Loan [Member] | Special Mention [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Home Equity Loan [Member] | Accruing Substandard [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Performing [Member] | Loans to individuals [Member] | Residential mortgage [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		1,767,930
Performing [Member] | Loans to individuals [Member] | Residential mortgage [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	58,635
Financing Receivable, Originated, 2019	216,234
Financing Receivable, Originated, 2018	195,224
Financing Receivable, Originated, 2017	231,620
Financing Receivable, Originated, 2016	220,120
Financing Receivable, Originated, 2015 or Prior	496,676
Financing Receivable, Revolving	36,298
Financing Receivable, Revolving, Converted to Term Loan	352,870
Total	1,807,677
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		276,138
Performing [Member] | Loans to individuals [Member] | Residential mortgage [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	286
Financing Receivable, Originated, 2017	38
Financing Receivable, Originated, 2016	205
Financing Receivable, Originated, 2015 or Prior	1,859
Financing Receivable, Revolving	246
Financing Receivable, Revolving, Converted to Term Loan	835
Total	3,469
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		78
Performing [Member] | Loans to individuals [Member] | Residential mortgage [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	94
Financing Receivable, Originated, 2016	2,155
Financing Receivable, Originated, 2015 or Prior	277
Financing Receivable, Revolving	40
Financing Receivable, Revolving, Converted to Term Loan	122
Total	2,688
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		2,404
Performing [Member] | Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	1,459
Financing Receivable, Originated, 2018	8,321
Financing Receivable, Originated, 2017	13,353
Financing Receivable, Originated, 2016	28,986
Financing Receivable, Originated, 2015 or Prior	140,765
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total	192,884
Performing [Member] | Loans to individuals [Member] | Personal [Member]
Recorded Investment [Abstract]
Non-Graded, Recorded Investment		84,853
Performing [Member] | Loans to individuals [Member] | Personal [Member] | Pass [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	48,145
Financing Receivable, Originated, 2019	234,882
Financing Receivable, Originated, 2018	88,016
Financing Receivable, Originated, 2017	115,576
Financing Receivable, Originated, 2016	74,987
Financing Receivable, Originated, 2015 or Prior	103,717
Financing Receivable, Revolving	505,951
Financing Receivable, Revolving, Converted to Term Loan	3,000
Total	1,174,274
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,116,196
Performing [Member] | Loans to individuals [Member] | Personal [Member] | Special Mention [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	30
Financing Receivable, Originated, 2018	37
Financing Receivable, Originated, 2017	50
Financing Receivable, Originated, 2016	49
Financing Receivable, Originated, 2015 or Prior	455
Financing Receivable, Revolving	2
Financing Receivable, Revolving, Converted to Term Loan	0
Total	623
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		45
Performing [Member] | Loans to individuals [Member] | Personal [Member] | Accruing Substandard [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	264
Financing Receivable, Originated, 2018	9
Financing Receivable, Originated, 2017	0
Financing Receivable, Originated, 2016	0
Financing Receivable, Originated, 2015 or Prior	0
Financing Receivable, Revolving	19
Financing Receivable, Revolving, Converted to Term Loan	0
Total	292
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		143,554
Non-Graded, Recorded Investment		37,398
Nonperforming Financial Instruments [Member] | Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		115,379
Non-Graded, Recorded Investment		37
Nonperforming Financial Instruments [Member] | Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		91,722
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial [Member] | Energy [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	3,802
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	0
Financing Receivable, Originated, 2016	0
Financing Receivable, Originated, 2015 or Prior	28,899
Financing Receivable, Revolving	63,747
Financing Receivable, Revolving, Converted to Term Loan	0
Total	96,448
Nonperforming Financial Instruments [Member] | Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		4,480
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial [Member] | Healthcare [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	29
Financing Receivable, Originated, 2019	37
Financing Receivable, Originated, 2018	535
Financing Receivable, Originated, 2017	0
Financing Receivable, Originated, 2016	0
Financing Receivable, Originated, 2015 or Prior	2,935
Financing Receivable, Revolving	534
Financing Receivable, Revolving, Converted to Term Loan	0
Total	4,070
Nonperforming Financial Instruments [Member] | Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		7,483
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial [Member] | Services [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	2,633
Financing Receivable, Originated, 2016	1,167
Financing Receivable, Originated, 2015 or Prior	3,931
Financing Receivable, Revolving	694
Financing Receivable, Revolving, Converted to Term Loan	0
Total	8,425
Nonperforming Financial Instruments [Member] | Commercial [Member] | General business [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	1,980
Financing Receivable, Originated, 2018	4,928
Financing Receivable, Originated, 2017	1,100
Financing Receivable, Originated, 2016	1,344
Financing Receivable, Originated, 2015 or Prior	161
Financing Receivable, Revolving	154
Financing Receivable, Revolving, Converted to Term Loan	14
Total	9,681
Nonperforming Financial Instruments [Member] | Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		1,163
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		10,133
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial [Member] | Public finance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		398
Non-Graded, Recorded Investment		37
Nonperforming Financial Instruments [Member] | Commercial real estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		27,626
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	232
Financing Receivable, Originated, 2016	7,484
Financing Receivable, Originated, 2015 or Prior	829
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total	8,545
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Residential construction and land development [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		350
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		18,868
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Office [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		6,858
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		909
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Commercial real estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		641
Non-Graded, Recorded Investment		0
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		493
Non-Graded, Recorded Investment		19,948
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Permanent Residential Mortgage [Member] | US Government Agency Insured Loans [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Non-Graded, Recorded Investment		6,100
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Home Equity Loan [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		0
Non-Graded, Recorded Investment		11,081
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Residential mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		493
Non-Graded, Recorded Investment		37,129
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Residential mortgage [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	31
Financing Receivable, Originated, 2018	491
Financing Receivable, Originated, 2017	322
Financing Receivable, Originated, 2016	1,039
Financing Receivable, Originated, 2015 or Prior	26,039
Financing Receivable, Revolving	658
Financing Receivable, Revolving, Converted to Term Loan	2,141
Total	30,721
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Residential mortgage [Member] | US Government Agency Insured Loans [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	0
Financing Receivable, Originated, 2018	0
Financing Receivable, Originated, 2017	0
Financing Receivable, Originated, 2016	0
Financing Receivable, Originated, 2015 or Prior	5,005
Financing Receivable, Revolving	0
Financing Receivable, Revolving, Converted to Term Loan	0
Total	5,005
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Personal [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment		56
Non-Graded, Recorded Investment		$ 232
Nonperforming Financial Instruments [Member] | Loans to individuals [Member] | Personal [Member] | Nonaccruing substandard and doubtful [Member]
Financing Receivable, Credit Quality Indicator Line Items [Abstract]
Financing Receivable, Originated, 2020	0
Financing Receivable, Originated, 2019	57
Financing Receivable, Originated, 2018	53
Financing Receivable, Originated, 2017	24
Financing Receivable, Originated, 2016	62
Financing Receivable, Originated, 2015 or Prior	50
Financing Receivable, Revolving	31
Financing Receivable, Revolving, Converted to Term Loan	0
Total	$ 277